Plastic Injection Molding

Typical applications

• Structural and functional components for industrial equipment enclosures and housings
• Precision components for medical device assemblies (see Medical Injection Molding)
• Consumer and commercial product housings, brackets, and mechanisms
• Electrical and electronic component carriers and connector bodies
• Insert-molded and overmolded parts combining plastic with metal or elastomer

Process overview

1. 1

   Quote & DFM review

   We review your model or drawing for moldability — wall thickness, draft, gate location, and tolerance feasibility — before quoting tooling.

2. 2

   Tool design & build

   Mold design is completed and reviewed with you before steel is cut; builds happen in our tool room or through a managed transfer from an existing supplier.

3. 3

   First-article production & inspection

   Initial shots are measured against your print and documented before the tool is released to production.

4. 4

   Production molding

   Parts run to your specified quantities and delivery schedule, with in-process quality checks at defined intervals.

5. 5

   Secondary operations & shipment

   Parts move directly into machining, finishing, pad printing, or assembly as needed, then ship complete.

Materials

• Nearly all thermoplastic resins — ABS, MABS (clear ABS), PP, PE (LDPE, LLDPE, HDPE), nylon (PA6, PA66, PA12) including glass-filled, PC and PC/ABS, acetal (POM), PS, acrylic, TPE/TPU, and others
• Glass fill up to roughly 30–35%. Above that we will decline the job — heavily filled resins damage the screws and barrels
• We do NOT process thermoset materials
• We do NOT process rigid (hard) PVC, liquid silicone rubber (LSR), or PEEK
• Nearly any color: blended in-house, pre-colored from a coloring house, or a standard base resin color — see Injection Molding Materials
• Regrind: we do not routinely regrind. Where it is used at all it is capped well below industry norms, and medical parts run virgin only, with no regrind whatsoever
• Material must be dried before running — typically 2–3 hours ahead of production. Drying and blending carry a small handling charge already built into the quoted price

Part design considerations

• Uniform wall thickness to reduce sink, warp, and cycle time
• Draft angle appropriate to texture and material shrink rate
• Gate location and type relative to cosmetic surfaces and fill pattern
• Rib and boss design to avoid sink marks on show surfaces
• Tolerance stack-up across mating and assembled components
• SPI surface finish callout for core and cavity surfaces — required on every new part
• Part size, projected area, and shot weight must suit an available press (1.45–80 oz shot range)
• Clamp tonnage is driven by projected area — roughly 3–5 tons per square inch, plus about 10% more per inch of depth beyond the first inch. Deep parts need far more tonnage than their footprint suggests
• Cooling dominates the cycle — typically around 80% of a ~50 second cycle — so wall thickness drives cost more directly than most people expect

DFM guidance

• A tool is cut for one specific resin's shrink rate. You cannot simply swap to a different material later and expect the same dimensions — a resin change usually means reworking steel
• We flag thick sections, sharp internal corners, and undercuts during quoting, not after tooling is cut
• Draft and radius recommendations are matched to your chosen resin's shrink behavior
• Where a design change would meaningfully reduce tooling cost or cycle time, we present the tradeoff before you commit to tooling
• See Injection Molding DFM for detailed design guidelines
• Every new plastic part needs the exact material identified and an SPI surface finish callout before tooling — a tool is cut to a specific finish and a specific shrink rate
• Most of our tooling is cold runner; hot runner tools can be built if specified at RFQ
• Mold temperature is controlled with chilled water or water heated below boiling — we do not run hot oil

Quality controls

• Parts produced to SPI standards, including SPI mold surface finish classifications
• First-article inspection against the customer print
• In-process dimensional checks at defined production intervals
• Documented inspection records available on request
• Additional documentation packages for regulated and medical-related work — see Quality & Certifications

Secondary operations available

• CNC machining of molded features (drilling, tapping, trimming)
• Pad printing and product decoration
• Ultrasonic welding and mechanical assembly
• Custom packaging on request

Frequently asked questions